Free volume characteristics on water permeation and salt rejection of polyamide reverse osmosis membranes investigated by a pulsed slow positron beam
Free volume characteristics on water permeation and salt rejection of polyamide reverse osmosis membranes investigated by a pulsed slow positron beam
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DOI：
10.1007/s10853-018-2740-3
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发表时间：
2018-07
影响因子：
4.5
通讯作者：
Jingjing Li;Bangyun Xiong;Chongshan Yin;Xiaowei Zhang;Yawei Zhou;Z. Wang;P. Fang;Chunqing He
中科院分区：
文献类型：
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作者：
Jingjing Li;Bangyun Xiong;Chongshan Yin;Xiaowei Zhang;Yawei Zhou;Z. Wang;P. Fang;Chunqing He
以不同含量的间苯二胺、三甲氧基氯和二甲基亚砜(DMSO)为前驱体，通过界面聚合，在多孔聚砜载体上制备了聚酰胺薄膜复合反渗透膜。基于脉冲慢正电子束的正电子湮没寿命谱对具有非均匀多层结构的膜进行了深度剖析，通过对o-ps强度随深度变化的结果进行拟合，可以估算出聚酰胺活性层的厚度。评价了膜的聚酰胺选择性层的自由体积特性，并与渗透性能进行了关联。随着DMSO含量的增加，平均自由体积尺寸(VFV)增大，这是水和氯化钠渗透增强的原因。然而，盐截留率显著降低，VFV略有增加，接近88.0°3的临界值，这是水合钠离子和氯离子的平均尺寸。这很好地解释说，扩大的自由体积分布使更大的自由体积参与到盐的渗透中，尽管VFV几乎没有变化。
Polyamide thin film composite reverse osmosis membranes on porous polysulfone support were prepared using m-phenylenediamine, trimesoyl chloride and dimethyl sulfoxide (DMSO) with various contents as precursors via an interfacial polymerization. The membrane with heterogeneous multilayer structure was depth-profiled by positron annihilation lifetime spectroscopy based on a pulsed slow positron beam and the thickness of the polyamide active layer can be estimated through fitting the results of depth dependence ofo-Ps intensity. The free volume characteristics in the polyamide selective layer of the membranes were evaluated and were correlated with the permeation properties. With increasing DMSO content, mean free volume size (VFV) was enlarged, which was responsible for the enhanced water and sodium chloride permeation. However, the salt rejection was significantly decreased with a slight increase in theVFVaround a critical value of 88.0 Å3, which was the average size of hydrated sodium and chloride ions. It was well interpreted for that the broadened free volume distribution enables an amount of larger free volumes to be involved in the salt permeation, although little change inVFVwas found.